ARMY TM 9-2805-257-14 AIR FORCE TO 38G2-103-2 NAVY NAVFAC P-8-612-14E c. Service.  Operations required periodically to keep an item in proper operating condition, i.e., to clean (includes  decontaminate),  to  preserve,  to  drain,  or  to  replenish  fuel,  lubricants,  hydraulic  fluids,  or  compressed  air supplies. d. Adjust. To maintain within prescribed limits, by bringing into proper or exact position, or by setting the operating  characteristics  to  the  specified  parameters. e. Aline. To adjust specified variable elements of an item to bring about optimum or desired performance. f. Calibrate.  To determine and cause corrections to be made or to be adjusted on instruments or test measuring and diagnostic equipment used in precision measurement. Consists of comparison of two instruments, one of which is a certified standard of known accuracy, to detect and adjust any discrepancy inn the accuracy of the  instrument  being  compared. g. Install.  The act of emplacing, seating, or fixing into position an item, part, or module (component assembly) in a manner to allow the proper functioning of an equipment or system. h. Replace. The act of substituting a serviceable like type part, a subassembly, or module (component or assembly)  for  an  unserviceable  counterpart. i. Repair. The application of maintenance services (inspect, test, service, adjust, aline, calibrate, or replace) or  other  maintenance  actions  (welding,  grinding,  riveting,  straightening,  facing,  remachining,  or  resurfacing)  to restore  serviceability  to  an  item  by  correcting  specific  damage,  fault,  malfunction,  or  failure  in  a  part,  subassembly, module  (component  or  assembly),  end  item,  or  system. j. Overhaul.  That maintenance effort (service/action) necessary to restore an item to a completely serviceable  operational  condition  as  prescribed  by  maintenance  standards  in  appropriate  technical  publications (i.e., DMWR). Overhaul does not normally return an item to a like new condition. k. Rebuild. Consists of those services/actions necessary for the restoration of unserviceable equipment to a like new condition in accordance with original manufacturing standards. Rebuild is the highest degree of materiel maintenance applied to Army equipment. The rebuild operation includes the act of returning to zero those age measurements  (hours/miles,  etc.)  considered  in  classifying  Army  equipment/components. B-4.  Explanation  of  Columns  in  the  MAC,  Section  II. a. Column (1). Group Number. Column 1 lists functional group code numbers which are assigned to identify maintenance  significant  components,  assemblies,  subassemblies,  and  modules  to  their  next  higher  assembly. b. Column (2). Component/Assembly. Column  2  contains  the  item  names  of  components,  assemblies, subassemblies, and modules for which group numbers (column 1) are assigned and for which maintenance is authorized. c.   Column (3). Maintenace Function. Column 3 lists the functions to be performed on items listed in Column 2. (Function definitions are contained in paragraph A-3.) B-2